In the section that starts with "Edit /etc/krb5.conf", they mention a manual
configuration to the krb5.conf file for machines that will be leveraging AD users:
[realms]
IPA_DOMAIN = {
....
auth_to_local = RULE:[1:$1@$0](^.*@AD_DOMAIN$)s/@AD_DOMAIN/@ad_domain/
auth_to_local = DEFAULT
}
Is this still required for sssd 1.13.0 and above?

The actual requirement is MIT Kerberos 1.12+ where localauth plugin
support was added. Then, of course, SSSD with localauth plugin
implementation, which is SSSD 1.12.1+.